Exact determination of phase information in spin-polarized neutron specular reflectometry

Abstract.

A method is proposed to determine the complex reflection coefficient of any real scattering length density (i.e., in the case where there is no effective absorption, which is a good approximation for neutrons) in neutron specular reflectometry. The method makes use of a magnetic reference layer mediated between the substrate and an unknown sample and measurements of the polarization direction of the reflected beam or a suitable choice of polarization and reflectivity analysis of the reflected beam. It corresponds to the concept proposed recently, but has been derived in the formalism of the transfer matrix. The method is based upon relations between the polarization of the incident and reflected beams, and the transfer matrix elements of the unknown and known layers. Thus, in this manner, only by final polarization orientation measurement can we find the reflection coefficient of any unknown sample which is surrounded on both sides by a uniform medium. Apart from the final polarization orientation measurement of the reflected beam, which is hampered by complications in selecting the physical solution, we show that the reflection coefficient can be determined by more flexible ways using a suitable choice of possible measurements of reflectivity and polarization of the reflected beam. A schematic example is presented to illustrate the method.